How accurate are email validation services?

Here's the honest answer: Most reputable validation services claim 90-98% accuracy on typical domains. That sounds great until you send your first campaign and bounce rates don't match the promise. The gap? Accuracy depends heavily on domain type, and vendors don't always tell you that.

Standard domains (your company email address or a Gmail account) validate cleanly most of the time. But catch-all domains. those mail servers that accept everything and filter inbox-side. can't be verified without actually sending mail. Role-based addresses like info@company.com or support@company.com are even trickier because they exist, but the validator can't know if anyone's actually monitoring them. Throttled domains (servers that play dead to protect against spam) might refuse the validation check altogether, making the service guess.

Why does this matter? Because those 90-98% accuracy claims assume a 'normal' mailbox. Your list probably isn't normal. If you've got 20% catch-all domains and 15% role addresses, your real accuracy might be 20 points lower than the headline number.

Here's what you can't expect from any validator. Mailbox providers (Gmail, Outlook, Yahoo) don't share their active mailbox status publicly. No service can perfectly predict whether someone's still checking their inbox. A validator can confirm 'this address follows proper format and the domain has mail servers,' but it can't see inside the mailbox itself.

Before committing to a validation service, test it on a sample of your list. Use our free blocklist checker to see how your addresses break down by type, then ask the vendor how accurate they are on YOUR domain mix. That number matters way more than the generic 90-98% claim.